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Kukersite is a light-brown marine type
oil shale Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitut ...
of
Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The ...
age. It is found in the Baltic Oil Shale Basin in
Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, and ...
and North-West
Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eight ...
. It is of the lowest
Upper Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The ...
formation, formed some 460 million years ago. It was named after the German name of the Kukruse Manor in the north-east of Estonia by the Russian
paleobotanist Paleobotany, which is also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeogr ...
Mikhail Zalessky Mikhail Dmitrievich Zalessky (russian: Михаил Дмитриевич Залесский, ''Mikhail Dmitrievich Zalesskiy''; 15 September 1877 – 22 December 1946) was a Russian paleontologist and paleobotanist. His main focus was an investiga ...
in 1917. Some minor kukersite resources occur in sedimentary basins of Michigan, Illinois, Wisconsin, North Dakota, and Oklahoma in North America and in the Amadeus and
Canning Canning is a method of food preservation in which food is processed and sealed in an airtight container (jars like Mason jars, and steel and tin cans). Canning provides a shelf life that typically ranges from one to five years, although un ...
basins of Australia.


Baltic Oil Shale Basin

The Baltic Oil Shale Basin covers about . Main kukersite deposits are Estonian and Tapa deposits in Estonia, and Leningrad deposit in Russia (also known as Gdov or Oudova deposit). Other occurrences in Russia are Veimarn and Chudovo–Babinskoe deposits. The Estonian deposit, which covers about , is exploited industrially; the Tapa deposit is not accounted as reserves due its lower value which makes its extraction economically inexpedient. The Leningrad deposit was exploited industrially but operations have ceased.


Geology

Kukersite occurs within the Kukruse and Uhaku stages of the Viivikonna and Kõrgekallas formations, as an often calcareous layer. In northern Estonia there are a total of 50 oil shale layers of kukersite, of which six lowest form a thick mineable bed. In this part kukersite lies near the surface while southward and westward its depth increases and its thickness and quality decreases. Estonia's kukersite represents about 1.1% of global and 17% of European oil shale resources. The total kukersite resources in Estonia are estimated to be about 4.8 billion tonnes, including about 1 billion tonnes economically proven reserve, 0.3 billion tonnes economic probable reserve and about 3.5 billion tonnes uneconomical proven and probable reserve. Economically proven and probable reserves forms active resource, which is defined as mineable deposits with energy ratings of at least 35 
gigajoule The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied ...
s per square metre and calorific values of at least 8 MJ/kg, located in areas without environmental restrictions. Energy rating of the oil shale mining block is calculated as the sum of the products of thickness, calorific values and densities of all oil shale layers and
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms when ...
interlayers. Up to 50% of active resources are designated as recoverable. The Leningrad deposit consists of 3.6 billion tonnes of kukersite, including more than one billion tonnes of economically proven and probable reserves.


Composition

Estonian kukersite deposits are one of the world's highest-grade deposits with organic content varying from 15% to 55% with average more than 40%, and it has 65–67% conversion ratio into shale oil and
oil shale gas Oil shale gas (also: retort gas or retorting gas) is a synthetic non-condensable gas mixture ( syngas) produced by oil shale thermal processing (pyrolysis). Although often referred to as shale gas, it differs from the natural gas produced from shal ...
. Fischer Assay oil yield is 30 to 47%. Its organic matter has an atomic ratio of
hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxi ...
to carbon of 1.51 and the mean calorific value of kukersite is 3600 kcal/kg. The principal organic component of kukersite is
telalginite Telalginite is a structured organic matter ( alginite) in sapropel, composed of large discretely occurring colonial or thick-walled unicellular algae such as '' Botryococcus'', ''Tasmanites'' and '' Gloeocapsomorpha prisca''. Telalginite is present ...
, derived from the fossil
green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alga a ...
, ''Gloeocapsomorpha prisca'', which has affinities with the modern
cyanobacterium Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blue ...
, ''Entophysalis major'', an extant species that forms
algal mat Algal mats are one of many types of microbial mat that forms on the surface of water or rocks. They are typically composed of blue-green cyanobacteria and sediments. Formation occurs when alternating layers of blue-green bacteria and sediments are ...
s in inter-tidal to very shallow subtidal waters.
Matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** ''The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ( ...
s dominantly include low-
magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...
calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratc ...
, dolomite, and siliciclastic minerals. They are not rich in heavy metals. Kukersite was deposited in a shallow marine basin. It lays in the depth of .


See also

*
Oil shale in Estonia There are two kinds of oil shale in Estonia, both of which are sedimentary rocks laid down during the Ordovician geologic period. Graptolitic argillite is the larger oil shale resource, but, because its organic matter content is relatively ...
*
Oil shale geology Oil shale geology is a branch of geologic sciences which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels. Oil shale f ...
* Cannel coal *
Lamosite Lamosite is an olive-gray brown or dark gray to brownish black lacustrine-type oil shale, in which the chief organic constituent is lamalginite derived from lacustrine planktonic algae. In minor scale it also consists of vitrinite, inertinite, telal ...
*
Marinite Marinite is a gray to dark-gray or black oil shale of marine origin in which the chief organic components are lamalginite and bituminite derived from marine phytoplankton, with varied admixtures of bitumen, telalginite and vitrinite. Marinite de ...
*
Tasmanite Tasmanite is a sedimentary rock type almost entirely consisting of the prasinophyte alga ''Tasmanites''. It is commonly associated with high-latitude, nutrient-rich, marginal marine settings find in Tasmania. It is classified as marine type oil s ...
*
Torbanite Torbanite, also known as boghead coal or channel coal, is a variety of fine-grained black oil shale. It usually occurs as lenticular masses, often associated with deposits of Permian coals. Torbanite is classified as lacustrine type oil shal ...


References

{{Reflist Oil shale geology Geology of Estonia Geology of Russia Oil shale in Estonia Oil shale in Russia